My thoughts:
1) Avoid the situation! How do you get yourself into this situation that you need to call the function two times for the same work item ID? Can you handle the errors before call the function first time? Please give an example as Rick asked.
2) See what Modak answered. Can you debug the function when executed second time to see where it goes wrong? Some global variables will be populated when you execute the function first time, and then when you execute it second time, the variables already have a value, and they might cause this problem. Perhaps you will find out that some certain variable is causing the problem, and you might clear it before executing the function second time (but please be sure what you are doing - this is a bit tricky thing and might cause problems).
3) Do a quick scan into OSS. Perhaps there is a note for this? ( E.g. I found that one of the WAPIs didn't work unless I didn't call it two times in a row.)
4) Try to avoid this, but perhaps you can see if you can use some other function to restart the workflow second (or even both) time. For example I can see that your function calls SWW_WI_ADMIN_ERROR_RESTART. You could try to call this function. Eventually you might get the same result. And actually you should get a hint whether this approach will work or not, when you go through the step 2 (debug the function).
Regards,
Karri